Microtome



April 29, 1969 D, PERSlDSKY ET'AL 3,440,913

MI CROTOME Filed Feb. 21, 1966 Sheet of 2 LADE AMF. START RETURN I SP I ED POWER i 24m n 59 40 4 4' F|G.5 07 \YB 0% LB J JA ' INVENTORS x Z MAXIMD.PERS|DSKY [3 WILLIAM J.ROACH 6 n 19 90? 5 Y 6 ATTORNEY United States Patent 3,440,913 MICROTOME Maxim D. Persidsky, San Francisco, and William J.

Roach, Hayward, Calif., assignors to Oxford Laboratories, San Mateo, Calif., a corporation of California Filed Feb. 21, 1966, Ser. No. 528,943 Int. Cl. B26d 7/06, /08

US. Cl. 83-422 5 Claims ABSTRACT OF THE DISCLOSURE The present microtome reciprocates a knife edge along an arcuate path at high velocity, thus performing many transverse movements of the blade while cutting a single slice of material, thereby enabling the instrument to cut a specimen without the necessity of freezing the same or embedding the same in paraffin, both of which steps are injurious to the spcecimen since distortion takes place when the knife hits the specimen head-on.

This invention relates, generally, to improvements in microtome sectioning systems of the type producing specimen sections for use with optical microscopes and the invention has reference, more particularly, to a novel microtome adapted for sectioning biological and other materials without the necessity of freezing or paraffin embedding of the material, thus eliminating the distortions and other deleterious effects inherent in such procedures.

Heretofore, it has been generally necessary in obtaining thin specimen sections of the order of five microns to freeze the specimen or embed the same in paraffin or other supporting materials, because microtomes as heretofore constructed generally advance the cutting edge directly against the material being sectioned thereby cutting the same by impact, with the result that, unless the material is embedded or frozen, it is subject to distortions, abrasions and non-uniform cuts, thereby rendering the specimen unusable in most cases unless so supported. However, freezing the specimen or supporting the same in paraffin or other materials ofttimes changes the nature of the specimen and renders it difficult or impossible to make a proper analysis thereof. The applicants have been experimenting for some years to extend the art of thin sectioning to the cutting of soft fresh tissue without restoring to fixation, embedding or freezing, the benefit from which is quite obvious. Thin sectioning of untreated fresh tissue is of great value in histology, histochemistry, enzimology, fluorescent techniques for the study of antibodies, incorporation of labeled compounds, and many other fields of importance. Since the penetrating pressure of the cutting edge seems to be a major limiting factor in sectioning soft tissue due to the elastic deformation it causes, applicants have conceived the present novel microtome using a knife blade moving on a portion of a circular arc to reduce such pressure and increase the knifes penetrating power.

The principal object of the present invention is therefore to provide a novel microtome or sectioning system that employs a cutting action wherein the knife edge used is caused to move transversely with respect to the specimen as it penetrates the same moving along an arcuate path, thereby greatly reducing the effective facet or cutting edge angle of the knife so as to thus shear the specimen with a minimum of direct pressure and producing slices that are not distorted or injured by the movement of the knife therethrough so that specimen need not be embedded or frozen but simply held or capsulated during the sectioning operation.

A feature of the present invention is to provide a novel microtome of the above character wherein the cutting edge is caused to move along a reciprocating arcuate path during its cutting movement, said path being substantially tangential to the specimen being sectioned at the midpoint of the movement of the cutting edge at which point the cutting edge has the greatest penetration and highest rate of movement, the cutting edge gradually being pulled back from the specimen as it approaches the ends of its reciprocating movement, whereby as the blade motion slows the cutting action also decreases, thereby producing perfect specimens.

Other features and advantages of the present invention will become more apparent after a perusal of the following specification taken in connection with the accompanying drawings wherein:

FIG. 1 is a plan view with parts broken away of the novel microtome of this invention;

FIG. 2 is a sectional View taken substantially along line 22 of FIG. 1;

FIG. 3 is a fragmentary sectional view taken substantially along line 33 of FIG. 1;

FIG. 4 is an enlarged fragmentary view taken along line 4-4 of FIG 1; and

FIG. 5 is a schematic plan view of the blade holder supporting means.

Similar characters of reference are used in the above figures to designate corresponding parts.

Referring now to the drawings, the reference numeral 1 designates the microtome housing having a pair of spaced upright extensions or support casings 2 and 2 projecting upwardly from the top thereof, within which casings are positioned a pair of precision machined leaf springs 4 and 4' that are fixedly attached at their rear ends as by screws 5 to the inner walls of casings 2 and 2'. The leaf springs 4 and 4 have the same dimensions and physical characteristics and have fixed upon their forward ends the opposite end portions of a supporting member 3 shown as a tubular shaft carrying a blade holder 17 centrally thereof. The end portions of shaft 3 project beyond the springs 4 and 4' and enter microphone armature structures 6 and 6' similar to the type used in dynamic loudspeakers. The end portion of shaft 3 within microphone armature 6' carries a coil coacting with a Surrounding permanent magnet to generate voltages responsive to the longitudinal movement of the shaft 3, whereby this structure acts as a sensing generator. This shaft 3, being supported upon springs 4 and 4', is free to oscillate along its longitudinal axis due to the transverse flexure of the springs 4 and 4' in use. The output of microphone armature or sensing generator 6' is shown fed through a phasing circuit 7, amplifier 8 and amplifier volume control 9 controlled from knob 15 on control panel 38 to the coil of microphone armature 6, whereby this armature, coacting with its surrounding magnet, serves to drive the left-hand end portion of shaft 3 as viewed in FIG. 1 in response to motions of the shaft as detected by microphone armature 6'.

Thus, microphone armature 6 acts as a timing or sensing generator and armature 6 serves as a motor for driving the shaft 3 to enhance the amplitude of its motion, its frequency of oscillation being determined by the natural frequency of the moving system, i.e., springs 12, 12', shaft 3, etc. Such frequency of the order of 45 to 137 cycles per second is varied at will by varying the effective lengths of the springs 4 and 4'. The effective lengths of these springs are adjustable by means of adjustable clamps 10 and 10' through which screws 11 and 11 pass. These screws also pass through longitudinal slots 12 and 12' in springs 4 and 4 and through similar slots 13 and 13' in the walls of extensions 2 and 2 and have knurled nuts 14 and 14 threaded on the outer ends of these screws for binding the springs 4 and 4' at suitable points along the lengths of the slots 12 and 12 as indicated by scales 3 28 (FIG. 4) to thereby vary the effective lengths of these springs and hence the frequency of oscillation of the shaft 3. The shorter the effective lengths of the springs, the higher the frequency of oscillation of the shaft 3.

The shaft 3, while oscillating, will remain parallel to its position when stationary but will move somewhat rear- Wardly as illustrated in FIG. 5 from its central stationary position. Thus, the blade holder 17 in use has a compound movement which is peculiar to the microtome of this invention and found essential in producing good sections. The static state of the spring suspension is shown in position A. It will be noted that the shaft 3 unites the left and right springs 4 and 4' so that movement of one spring results in exactly the same movement of the other. As the driving motor 6 moves this shaft 3 from central position A to the right to position B, as viewed in FIG. 5, the shaft is also displaced the distance X to the rear, and similarly when the shaft 3 moves from its central position A to the left to position C. The result of these two movements of the shaft causes the blade holder 17 to transcribe a small arc. With the springs 4 and 4' having the same effective lengths, the angle 0 between the front plane of the blade holder 17 and the center line shown remains a constant ninety degrees at all positions of the blade holder.

During a vibratory cycle, the speed of blade 18 carried by blade holder 17 is zero at both position B and position C and accelerates to a maximum speed at position A. An increase in amplitude will of course increase displacement YY, displacement X, and maximum blade speed. With an increase in frequency caused by shortening the effective spring length, if displacement YY is held constant, the maximum blade speed and displacement X will be increased. Thus, an infinite number of blade movements are possible by varying amplitude and frequency, and a satisfactory combination of variables can be determined by experiment for each tissue. In practice it is usually possible to produce satisfactory sections at frequencies and amplitudes varying a setting or two from the optimum on scale 28.

The blade amplitude knob on control panel 38 is shown connected schematically in FIG. 1 for operating the amplifier volume control 9 to thereby vary the amplitude of movement of the shaft 3, although this adjustment does not vary the frequency of oscillation of the shaft. The blade holder 17 is adjustably mounted upon shaft 3 and can be turned angularly about the longitudinal axis thereof so as to vary the angle of cut of the cutting edge or blade 18 at will, this cutting edge being preferably a suitable razor blade, although other types of cutting edges can be used. The blade 18 is adapted to engage a specimen (not shown) supported upon a suitable holder such as 20 carried by a specimen post 19 contained within a bath 29 supported upon the top 30 of a movable carriage 31 having depending guide rails 32 slidable in guides 33 fixed within housing 1, the guides 33 permitting the carriage 31 to move the specimen post and its supported specimen toward and away from the blade 18.

The carriage 31 is adapted to be reciprocated by a reversible motor 34 operating through a pinion 35 driving a rack 36 on the carriage 31, the speed of the carriage 31 and hence that of the specimen being determined by a control knob 37 mounted on control panel 38. Thus, this speed may conveniently be from a few centimeters per minute to several thousand centimeters per minute. Push button switches 39 and 40 on panel 38 control the advancing and returning movements of the carriage 31. By pushing button 39, the carriage 31 is caused to advance the specimen positioned in bath 29 toward the vibrating blade 18 to be sectioned thereby, while pushing button 40 returns the carriage at a higher speed toward the front of the instrument, i.e., downwardly as viewed in FIG. 1, to remove the specimen from the blade which, during the return movement of the carriage, is no longer vibrating suitable relays (not shown) within housing 1 serving to control this action. Push button 41 on the control panel 38 is the power on and off switch of the instrument.

Specimen post 19 is shown in the drawings as supporting a vacuum holder 20 having a perforated disc top 21. When using the vacuum holder 20, suction is applied to the interior thereof from a vacuum source or pump (not shown) so that the specimen placed upon the perforated top 21 is retained thereon by the vacuum within the holder 20. The specimen ordinarily need not be frozen or embedded in reinforcing materials such as paraffin for this purpose.

The post 19 extending downwardly through bath 29 is adapted to be raised and lowered by means of a motor 22 mounted on carriage 31. Motor 22 acting through drive gearing 23 turns a nut 24 within a tubular support casing 25, nut 24 serving to move vertically a threaded extension 26 fixed upon the lower end of the non-turnable post 19 mounted within the casing 25 so that this post can be raised or lowered depending on the direction of rotation of motor 22. This motor is controlled from a snap switch 42 on the carriage top 30, the direction of movement of this switch determining the direction of movement of the post and specimen Whether up or down. The motor 22 provides a relatively fast vertical movement of the specimen, as where thick sections of microns or greater are to be sliced. The post 19 is shown carrying a trip arm 27 for actuating-limit switches 48 which serve to limit the vertical movement of the post 19 in use, lamps 46 and 47 on carriage top 30 serving to indicate when the post 19 is at the upper limit or lower limit of its travel as the case may be.

Ordinarily, a section thickness control knob 43 that is manually turned serves for cutting sections of less than 100 microns. This knob 43 turns shaft 44 that acts through gearing 45 to turn the nut 24 to raise or lower the specimen post 19 and hence the specimen. The thickness of a section can be read directly from the micron counter 48 on top of knob 43.

In operation, the specimen is placed on holder 20 or other holder mounted on post 19, and liquid such as water poured into bath 29 so that the blade edge is immersed, and, having set the desired blade frequency by adjusting knobs 14 and 14' along scales 28, the blade amplitude by adjusting knob 15, the specimen speed by adjusting knob 37, and having set the blade angle by turnably adjusting holder 17 on shaft 3, the start button 39 is pressed, thereby moving the specimen into the vibrating blade 18. When the blade has passed through the specimen, the return button 40 is pressed to return the specimen carriage 31 and stop the vibrating knife 18. The section will float clear of the specimen. Extremely soft specimens may need to be capsulated in some support media such as agar, gelatin or alginate before sectioning. The liquid in bath 29 prevents heating or drying of the specimen.

The movement of the knife 18 along a curved path transverse of the specimen not only greatly reduce the penetrating pressure of the same since the effective facet or cutting angle is reduced and the blade enters the specimen at less than its top speed, attaining greater transverse speed as it moves toward its center of oscillation, thereby taking advantage of low sliding friction in the area of greatest cutting and then widthdrawing or pulling back from the specimen as it approaches the limit of its travel in either transverse direction, but also produces a sharp, regular and uniform cut with minimum distortion of the specimen in use and enables the cutting of most specimens without the necessity of embedding, fixing or freezing the same.

Since the reciprocating cutting edge of the blade enters the specimen at an acute cutting angle and not in a directly head-on collision as in prior art devices, there is no distortion of the specimen. It will be noted that the blade 18 sweeps across the specimen substantially tangentially to the same and makes a great many transverse movements in opposite directions as it gradually passes through the specimen in cutting a single slice of the latter, thus providing a gradual penetration of the specimen by the blade so as to produce perfect undistorted specimens.

Since many changes could be made in the above construction of the novel microtome of this invention and many apparently widely different embodiments of this invention could be made Without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A microtome comprising a housing, a pair of mutually spaced similar leaf springs having corresponding end portions fixedly supported upon said housing, a linear knife supporting member extending between the other end portions of said leaf springs and attached thereto, a specimen holder, a carriage carrying said specimen holder, said carriage being movable for advancing said specimen holder and specimen carried thereby toward a knife carried by said supporting member, and driving means connected for oscillating said supporting member along its linear axis and hence the connected leaf springs to effect movement of the knife carried thereby along a reciprocating arcuate path, the knife oscillating back and forth many times as it gradually penetrates the specimen While cutting a single slice of the same to thereby section the specimen with a minimum of distortion.

2. A microtome comprising a housing, a pair of mutually spaced similar leaf springs having corresponding end portions fixedly supported upon said housing, a knife supporting member extending between the other end portions of said leaf springs and attached thereto, a specimen holder, a carriage carrying said specimen holder, said carriage being movable for advancing said specimen holder and specimen carried thereby toward a knife carried by said supporting member, driving means connected for oscillating said leaf springs and said knife supporting membet to effect movement of the knife carried thereby along a reciprocating arcuate path to thereby section the speciment with a minimum of distortion, means for changing the effective lengths of said leaf springs to vary the frequency of oscillation of said knife supporting member, said driving means comprising a microphone armature connected to said knife supporting member for actuating the same, a sensing microphone armature driven from said knife supporting member for producing a sensing signal responsive to the frequency of oscillation of said springs and connected knife supporting member, and control means connected to said sensing microphone armature for causing said sensing signal to effect operation of said driving microphone armature.

3. A microtome as defined in claim 2 wherein said control means comprises an amplifier for receiving said sensing signal and for supplying an amplified version of the same to said driving microphone armature for effecting oscillation of said knife supporting member, and an adjustable volume control for said amplifier connected to vary the amplitude of motion of said knife supporting member for varying the width of cut of the knife.

.4. A microtome as defined in claim 2 comprising a bath supported on said carriage and movable therewith for surrounding said specimen holder with liquid, means for advancing and retracting said carriage at controlled speeds for effecting sectioning of a specimen while immersed in said bath liquid, and dual automatic and manual control means for raising and lowering said specimen holder at variable speeds to obtain rapid selective thicknesses of sectioning at will.

5. A microtome as defined in claim 4 wherein said specimen holder comprises a vacuum holder having a perforated upper surface for securing a specimen thereto without the necessity of enclosing the specimen in rigid material, thereby preventing distortion of or injury to the speclmen.

References Cited FOREIGN PATENTS 86,567 11/ 1958 Denmark. 743,212 12/1943 Germany. 913,112 6/1954 Germany. 843,477 8/ 1960 Great Britain.

OTHER REFERENCES Cocks et a1.: A Cantilever Microtome for Precision Sectioning in Electron and Light Microscopy, November 1952, The Review of Scientific Instruments, vol. 23, No. 11, pp. 615-618.

WILLLIAM S. LAWSON, Primary Examiner.

US. Cl. X.R. 83607, 915.5 

